This invention relates to the constrained drying and/or heat treatment of a continuous web stock of film.
In the production of continuous rolls of film it is sometimes necessary to separate the film from its solvent. This separation process is known as drying of the wet film. Drying of wet film often causes the film to shrink. As this shrinkage is normally undesirable, it is necessary to constrain the drying film so that it retains a usable shape. Another process step in the production of continuous rolls of certain types of film is to heat treat a dry film to improve certain of the film's properties. Heat treatment may also result in film shrinkage. In order to dry and/or heat treat a roll of continuous film it is necessary to be able to move the roll of film in a continuous, non-interrupted manner.
Current equipment that exists to handle ("handle" meaning to move or to dry or to stretch or to heat treat) continuous rolls of film or other web stock materials involve either intricate and/or expensive clamping means to hold the film (U.S. Pat. No. 3,571,846) or a gripping means that involves puncturing the film (U.S. Pat. No. 3,160,340). U.S. Pat. No. 3,240,412 describes an arrangement for moving tensioned webs of foil where the foil has flanged edges.
There is a need for a simple, inexpensive apparatus for the drying and/or heat treating of a continuous web stock of film (with up to 99% solvent in the wet film) while the film is in an unpunctured and constrained, though unstretched, state.